Safety paper



2, 1933. B. w. SMETH h s SAFETY PAPER Filed Jan. 16, 1931 TANA QD'SALESCQMPANY ANYWHERE U-S-A. No.

PAY TO THE ORDER OF 11 FIRST NATIONAL BANK ANYWHERE, U.S.A.

INVENTOR BURGESS W SMITH BY I.

Patented 2, 319333 UNHTED ters orrica or noeiansrnn, new roan, inssrenonro rm ronn coarser-tr, and, or nocmsrnn, nnw roan, a eonronnrron or newroan sarnrr Application filed January it, ion,

This invention relates to safety paper such as commonly em loyed for themaking of bank checks, dra ts, bonds and other valuable instruments andmore particularly to s the variety of such paper containing a sensi=tive chemical ingredient capable of reacting with a chemical eradicatingmeans to develop a conspicuous stain or color and thus indicate anunauthorized attempt to alter to matter written on such paper.

@no object of the invention is to provide such a paper containing animproved sensitive ingredient which is relatively stable to normalinfluences, but quickl develops a con- 1 trasting color change with thechemical eradicators in common use, in either an acid or alkalinecondition, and capable after such color change, of resisting removal bythe agents commonly employed for such pur oses.

A further object is to provide a safety paper, of the above character,capable of be ing manufactured by a comparatively simple and practicablemethod and at a comparatively low cost,

A further object is to rovide such a paper having a surface thereorinted with an ink containing a sensitive su stance of the char actordescribed to form one or more initially colorless and inherently warningsymbols adapted to be conspicuousl developed in color upon theapplication oi chemical eradi= caters in common use,

To these and other ends the invention re= sides in certain novelfeatures and improve= ments, all as hereinafter more fully described,such novel features and improvements being pointed out in the claims atthe end of the specification.

In the drawing:

Fig. 1 shows a bank check embodying the present invention in one mode ofapplication of the same, and

Fig, 2 is a similar view showing a portion of the bank check with adifierent mode oi aplication of the invention in the preparation ofsafety paper of the character described in which the use of inkeradicators is indicated by the productions m a stain or other colorchange, the active In Serial Ito, EQQQTZQ.

gredient contained in the paper, for mash mum eiiiciency, should possesscertain important characteristics in a definite and substantial degree,to adord paper capable of functioning in a positive and reliable manneradapted to meet the exacting requirements, for example, of bank checksand similar value representing instruments. Among such requirements, theactive substance should be relatively stable to normal influences andthe stain when produced should reliably resist removal by reagentscommonly employed for such purposes. it should react quickly with thecommonly used ink eradicators which are generally composed of an alkalihypochlorite used in conjunction with an acid such as a solution oftartaric acid. It should iurthermore react regardless of whether theacid of the eradicator is used first or after the alkali hypochlorite orwhether it is used at all, as otherwise its efifectiveness could bereadily avoided,

There are a number of compounds which react to give a conspicuous stainwhen hypochlorite of soda is used alone or in other it words, in thealkaline condition as, for erample, manganese sulphate and a number ofaromatic amines. But when the hypochlorite of soda solution is usedafter the a plication of an acid solution and therefore in an acidcondition, practically no stain, or at least an insignificant one wouldbe produced,

In an efiort to overcome such and other defects or" active ingredientsheretofore one ployed in safety paper, it has been found that substancescharacterized by the presence of two benzene rings or groups of benzenerings, linked.- together with the diphenyl linkage or the e uivalent ofsuch linkage and having two hy roxyl radicals in the para position so tothat linkage, develop a conspicuous stain with eradicators comprisinghypochlorite of soda in either an alkaline or acid conditiona Substancesof this class are represented in the simplest form byp,p'dihydroxydiphenyl as and in a more com or form by p pdihy=droxydihenylsulfi e and p,pd1hydroaydi=- phenylt iourea, but anyequivalent linkage till t that does not dc'troy the diphenol character-1istics may be used, and the term diphenol its substance, using theshorter name, is employed herein and in the appended clalms as includingall such forms having essentially the characteristic structure ornucleus described above, as well as their substitution products,analogues, homologues and derivatives.

These diphenol substances have been found to possess to a high degreethe important qualities requisite for use in safety paper as previouslydescribed and have in addition the further advantage of being colorlessor substantially colorless, at least in a relatively pure form, so thatthey are for this reason also particularly advantageous in that theylend themselves to use in white or light colored safety paper, as wellas for printing on such paper an initially invisible warning symbol as,for example, the word Void, for development by an eradicator.

The simplest form of such substances named above is preferred as it isparticularly adapted for manufacturing purposes on a commercial scale ata low cost and in a high degree of purity. In using this form, it may bedissolved'in alcohol, or made into a water solution of one of its salts,preferably its sodium salt. The exact formula of either of thesesolutions is a matter of choice to suit particular conditions, theamount used being in substantial proportion to the intensity of thereaction color desired to be developed. Such a solution may be used toimpregnat/e or coat the paper and such application to the paper is arelatively simple matter presenting no dificulty to one skilled in theart. The solution may be incorporated in the paper at various stages ofmanufacture, for errample, by addition to the pulp or to the web orsizing. These solutions may be employed either with or withoutregenerating the original phenol by action of an acid and,alternatively, instead of using solutions as described, the base may beground and formed as a suspension and so incorporated in the paper.

Instead of impregnating or coating the whole surface of the paper, asindicated by the general stain developed by an eradicator as shown at 5,Fig. l of the drawing, or in add1tion thereto, the diphenol substancemay be made into an ink and used to print on the paper the warningsymbol such as the word Void, or other printed matter covering the papersurface in whole or in part, of an initially invisible character, butadapted to be rendered visible to act as a warning upon the applicationof an eradicator to any substantial portion of the paper surface. Thismode of application is indicated, for example, in Fig. 2 of the drawingwhere the paper is shown as having a background 6 printed on it, leavingunprinted portions 7 representing the letters of the warning word Void,the background being shown as neoeeaa developed by an eradicator. Suchan ink may be made in any suitable or known manner, as well understoodin the art, with varnishes or other vehicles regularly used for thispurpose, or celluloid dissolved in diacetone alcohol, or triacetin maybe used, the proportions being adapted to the particular printingprocess and apparatus desired to be employed.

Upon the application of the usual ink eradicators, such, for example, ashypcchlorite of soda in either an acid or alkaline condition, with orwithoutthe accompanying application of an acid, and in any order ofapplication, the diphenol substance reacts rapidly to develop a stain orchange of color contrasting sharply with the surrounding paper surface.Thus the application of the hypochlorite in an acid condition develops apronounced orange stain and when hypochlorite of soda is used alone orin an alkaline state, a pronounced purple bla-cl: stain is developed.Such stains are substantially permanent against the influence of light,moisture or temperature, and relatively insoluble.

The invention thus provides a safety paper having in a high degree thosequalities of sensitiveness in development and indelibility whendeveloped which are required for the protection of valuable instruments,such as bank checks, as well as a safety paper adapted for commercialproduction by practicable methods.

I claim:

1. A safety paper containing a substance characterized by two carbonrings or groups of carbon rings linked together with the diphenyl orequivalent linkage and having two hydroxyl radicals in the para positionto that linkage.

2. A. safety paper containing a colorless substance having two benzenerings or groups of benzene rings linked together with the diphenyl orequivalent linkage and having two hydroxyl radicals in the para positionto that linkage and adapted to react with chemical eradicating means todevelop a conspicuous stain or color.

3. A safety paper having a surface coated in whole or in part with anink comprising a substance having two benzene rings or groups of benzenerings linked together with the diphenyl or equivalent linkage and havingtwo hydroxyl radicals in the para position to that linkage, togetherwith a varnish or other vehicle in sultable proportions to adapt thesamefor printing on said paper.

4. A safety paper having a surface coated in whole or in part with aninitially colorless ink comprising a substance having two benzene ringsor groups of benzene rings linked together with the diphenyl orequivalent linkage and'having two hydroxyl radicals in the para positionto that linkage, and a vehineoaeae adapted to react with a chemicaleradicator to form a conspicuous stain or color.

5. A safety paper having an inherently warning symbol printed thereonwith a colorless ink comprising a substance having two benzene rings orgrou s of benzene rings linked together with the iphenyl or equivalentlinkage and having twohydroxyl radicals in the para position to thatlinkage, and

a vehicle, in suitable proportions for printing, the said ink beingadapted to react with a chemical eradicator to develop a conspicuouscolor change and thereby render said warning symbol conspicuouslyvisible.

6. A safety paper containing a diphenol substance adapted to react withchemical eradicating means to develop a conspicuous stain or color.

7. A safety paper containing the salt 0 a diphenol substance adapted toreact with chemical eradicating means to develop a conspicuous stain orcolor.

8. A safety paper-having a surface printed in whole or in part with anink compris ing a diphenol substance together with a vehicle in suitableproportions for printing.

9. A safety paper having an inherently warning symbol printed thereonwith a colorless ink containing a diphenol substance adapted to reactwith a chemical eradicator to develop a conspicuous color change andthereby render said warning symbol conspicuously visible.

10. A safety paper having an inherently warning symbol printed thereonwith a colorless ink containing a salt of adiphenol substance adapted toreact with a chemical eradicator to develop a conspicuous color changeand thereby render said warning symbol conspicuously visible. BURGESS W.SMITH.

